This invention relates to an apparatus for driving a syringe plunger into a barrel using manually created pneumatic pressure.
Many useful medical procedures and devices require the application of a controlled and sustained pressure. Medical devices such as angioplasty balloons, esophageal dilatation balloons, artificial urethral sphincters, and skin expanders all require the application of a sustained pressure that is both easy to apply and highly controllable.
Devices suitable for applying pressure to medical devices suffer from a number of disadvantages, including complexity, necessity of two handed operation, and the difficulty of precisely controlling the amount of pressure applied while using a standard medical syringe.
Fischione (U.S. Pat. No. 4,655,749) discloses an angioplasty pressure controller having a housing with a slidable pressure cylinder. A drive screw is connected to a piston in the cylinder and arranged for fine adjustment by turning the drive screw. This device has the disadvantage that two handed operation is required to operate the device.
Lundquist (U.S. Pat. No. 4,332,254) discloses a system for inflation and deflation of a balloon-type dilating catheter assembly utilized to perform percutaneous transluminal coronary angioplasty procedures. A primary syringe pump drives a secondary fluid pump mounted on the primary pump. The device has the disadvantage in that standard medical syringes cannot be used to supply an easily controllable, sustained pressure utilizing one-handed pumping operation. Reference is made to this prior art concerning the applicability of such apparatus in medical fields.
The present invention is an improvement over devices known in the prior art because inflation of medical devices requiring the application of pressure in excess of what is easily achievable for a sustained period of time by unaided manual force applied to a plunger in a syringe having a pressurizing fluid contained within its barrel are enabled by use of this apparatus.
An apparatus according to the present invention comprises means for holding a syringe barrel and means for holding an associated syringe plunger. A manually operated pneumatic driving means is used to apply force to the syringe plunger. The pneumatic driving means comprises a drive piston reciprocable in a sealed drive piston chamber. The drive piston is directly or through appropriate linkages capable of applying a sustained force to the syringe plunger.
A pumping system useful for incrementally increasing the pneumatic pressure in the drive cylinder chamber, and therefore also incrementally increasing the force applied by the drive piston to the syringe plunger, comprises a manually driven pumping piston capable of reciprocating action in a pumping chamber of a pumping chamber body. Air compressed by the action of the pumping piston during a compression stroke can travel through a pneumatic passage containing a unidirectional valve which only permits the outlet of pressurized air from the pumping chamber. The unidirectional valve between the pumping chamber and the cylinder chamber permits the gradual increase of pneumatic pressure in the cylinder chamber by repeated compressions of the manually driven pumping piston. This system gives the user excellent control over the amount of pressure applied to an inflatable medical device and the speed at which the pressure is applied. Both fast and slow inflation is enabled by a respective fast or slow manual pumping action.
The pumping piston has a connected piston handle for manually driving the piston into the pumping chamber. Entrained air is compressed to a pressure sufficient to open the unidirectional valve and allow pressurization of the drive piston chamber. The pumping piston is spring loaded to return the piston to an extended position in preparation for the next compression stroke. Additional air is admitted to the pumping chamber through an air intake valve or opening which closes on the compression stroke of the piston and opens on a return stroke during which the piston is retracted from the pumping chamber.